The line sweated and shuffled beneath sweeping curves of the UAE pavilion at the 2015 World Fair, the city of Milan distantly visible through the summer heat haze.
My water bottle ran out just as I reached the front of the queue. Fitting.
The show we'd waited for was as grandiose as the pavilion's design. I witnessed a story of a little girl transported through time from the back of her family's huge SUV. She experienced the heritage of her nation as it happened to her grandmother; a tiny desert tribe assailed by a lethal sandstorm, a pack of wolves, and a devastating water shortage. The girl fought valiantly through and saved her grandmother, who was in labour with the girl's mother (yes, it was convoluted). Together they planted a seed and it grew into a mighty palm tree. Back in the present, the cherished tree was dug up and lifted by helicopter to a new home on one of Dubai's artificial islands, allowing construction of a skyscraper where the tree stood.
Then the audience were encouraged to sing along as a wall-sized hologram of the little girl led a karaoke rap about water security.
I drifted out, mind spinning. What had I witnessed? Intergenerational ideals? A reminder of incredibly rapid societal change? Incoherent propaganda? Embedded in the show was a message about water, energy and arable land. I think.
Fortunately, there were taps to refill water bottles for free at the World Fair. I gulped down some cold liquid and found a place to sit and think.
Who is this all for?
I drifted through the World Fair's gaudy pavilions, full of shining 4K screens and giant nets to climb on and Ecuadorian birds that wanted me to dance and towers full of sachets of free Swiss coffee and dried apple. I felt utterly alienated. It was supposed to be about 'Food for the Future, Energy for Life', but couldn't work out who all of it was for. Families? Businesses? Governments? Tourists? It was targeting everyone and no-one.
I watched Italian-coloured smoke erupt from the Tree of Life. Some people cheered. The question opened itself wider in my mind.
Who is sustainability for?
Is it for solar micro-grid operators in Malaysia whose work enables locals to refrigerate vaccines and watermelons? Or shale gas drillers in Ohio whose industry is ousting coal from the US energy mix? Perhaps it's for packaging designers who stamp the vegan logo on a green container of minty shower gel.
Sustainability is a word that slips over existing agendas like a translucent glove. Remote communities in Malaysia need electricity. Drill operators wants a wage to live on. Packaging designers want vegans - heck, anyone - to buy their brand of gel. Sustainability appears when someone points to it, but how often is it there when our backs are turned?
A tiny proportion of people focus their lives, their work, their businesses on sustainability. It offers guiding principles, big ideas, a vision in the sky - one that, often, resists close-up scrutiny and slips through the cracks of messy, present-day reality.
I used to write science news. It taught me many things. One is that, to communicate an idea successfully, I must define my audience and tailor a message that's relevant to them.
Let's boil it down: Sustain. "Cause to continue for an extended period." Keep going. Perpetuate. Try, please, to make sure the future is roughly like it is today, or at least not worse.
Who is that message for? It is, fundamentally, opposite to how individual life progresses: we change, the world changes, we die.
There's a swath of good and important ideas bound up in the term sustainability. Let's be bold. Declare sustainability dead, its nebulous form riddled with worthy but impractical definitions, polluted with greenwash, weighed down by misconceptions and legalese and popular apathy and the curled lip of outspoken political naysayers. Let's break it open and pull free strong goals and vocabulary, distinct audiences, and actions to make the future better.
Strengthen. Support. Build. Improve. Nourish. Uphold. Restore. Promote. Protect.
The UN's new Agenda for Sustainable Development is a step toward this. Under the billowing banner of sustainability, it makes firm statements, outlines goals and exhorts action. Find a cause that motivates you. Make it yours. Articulate it, turn it over in your mind. Sustainability is not for everyone, but the future is. You control how you travel there. And you can take action as you live that journey.